1. Field of the Invention
The present invention relates to a lens barrel which collapses and stores lens groups therein when not in use, and protrudes the lens groups to predetermined positions when photographing. More particularly, the present invention relates to an optical system apparatus, a camera and a portable information terminal apparatus including a lens barrel suitable for a zoom lens unit which can change the focal distance by relatively moving a plurality of lens groups.
2. Discussion of the Background
With improvement in high performance of a photographing lens such as a zoom lens unit which is capable of changing the focal distance and in downsizing according to the user's demand as to an image pickup apparatus such as a digital camera, there is an increasing number of image pickup apparatus employing a so-called collapsing photographing lens unit in which lens cylinders are stored within a body of the image pickup apparatus when photographing is not carried out. Furthermore, since not only a simple reduction in dimensions but also a further reduction in a thickness of the image pickup apparatus are also demanded, it is now desired to reduce the thickness of a lens barrel portion in a collapsed state to a minimum limit.
As a technology to cope with the demand for reduction in the thickness of the image pickup apparatus, a collapsible construction has been used, in which the lens cylinders are stored into the body of the image pickup apparatus when the photographing is not carried out and in which a part of the lenses is evacuated from an optical axis of the lenses used in photographing, when the lens cylinders are collapsed and stored. Such a technology is disclosed, for example, in JP-A 2003-315861 and in JP-A 2003-149723. According to the structures disclosed in these Japanese unexamined patent application publications, since a part of the lenses is evacuated from the optical axis when the lens cylinders are stored, a dimension of the photographic lens unit in a direction of the optical axis can be reduced in the collapsed state, so that the thickness of the image pickup apparatus can be reduced.
Also, a lens barrier which can be opened or closed when the lens barrel is collapsed is incorporated in the image pickup apparatus such as in the camera utilizing the collapsing photographing lens mentioned above, to prevent dirt and dust from entering into a body of the camera, or to prevent the photographing lens or the like from being damaged. The lens barrier is classified into a lens barrel barrier and a body barrier. The lens barrel barrier is provided inside of the lens barrel and has a barrier blade. The body barrier is provided at a front of the lens barrel of the camera body and is slid or rotated to be opened and closed. The lens barrel barrier has the advantages that it occupies little space and it can easily be interlocked with the lens barrel. However, since a diameter of a lens arranged closest to a side of an object to be photographed is the largest in the photographing lens of a recent camera equipped with a wide-angle lens, the lens barrel becomes large when the lens barrel barrier is provided in the lens barrel in which the lens having the largest diameter is accommodated. For this reason, generally, many of the cameras equipped with the wide-angle lens utilize the body barrier.
The body barrier can be classified into an external barrier and an internal barrier. The external barrier is provided outside of a front cover of the camera body and is slid to be opened and closed. The internal barrier is arranged at a position inside of the front cover and the front of the lens barrel, and is slid or rotated to be opened and closed. In the external barrier, in most cases, the user slides a barrier manually to open and close the barrier, and power of the camera is turned on or off in accordance with the sliding operation of the barrier. On the other hand, the internal barrier can also be classified into a type having a barrier lever for opening and closing a barrier in which when the user manipulates the barrier lever, the barrier being opened or closed by an operation of a link mechanism coupled to the barrier lever and the power is also turned on or off correspondingly (hereinafter, referred to as “manual open-close barrier”), and a type having a main switch in which when the user presses the main switch down, the power is turned on or off and the barrier also opens or closes automatically at the same time (hereinafter, referred to as “automatic open-close barrier”).
Since it is necessary to make the opening and closing operations smooth in the body barrier, a space is provided between the front cover of the camera body and the body barrier. However, it is often the case that a rattling movement or an abnormal sound is produced when the user shakes the camera at the time that the camera is carried for example and is not used, due to the presence of the space. Accordingly, there is a camera having the external barrier in which a protrusion formed on a back surface of the external barrier mutually engages with a protrusion formed on the front cover of the camera body, only at the time when the external barrier is located at a closed position or at an evacuated position, so as to prevent the vertical rattling movement between the front cover and the external barrier. Such a technology is disclosed for example in JP-A 2001-228507.
Also, there is a camera having the external barrier with a curvature of a guide rail attached on a surface of an external package (front cover) of the camera body by which the external barrier slides and moves that curvature is made larger than a curvature of the external package of the camera body. Hence, according to this technology, the external barrier receives a force that pulls the external barrier toward a side of the camera body at the opening and closing ends of the external barrier, thereby preventing the external barrier from being rattled. Such a technology is for example disclosed in JP-A 2001-290196.
On the other hand, there is a camera having the automatic open-close barrier in which a detector for detecting that the user's finger touches the body barrier. When the detector detects that the finger of the user touches the body barrier at the time when the body barrier moves, the body barrier is moved to an opened position or the movement of the body barrier is stopped. Hence, a barrier mechanism and the lens barrel are prevented from being damaged, and simultaneously, the user's finger is also prevented from being caught by the barrier before it happens. Such a technology is disclosed in JP-A 2001-91993 for example.
However, in the structures disclosed in JP-A 2003-315861 and JP-A 2003-149723, the position of the lens evacuated from the optical axis is substantially within the lens cylinder which has the maximum outer diameter. Therefore, the lens cylinders contribute to a reduction in a thickness of the image pickup apparatus when the lenses are stored, but the outer diameter of the lens barrel increases. When compared with a case where the lens is not shifted from the optical axis, because the outer diameter of the lens cylinders increase, the dimensions of the lens cylinders, in particular, the dimensions of the lens cylinders as viewed in a plane orthogonal to the optical axis increase. As a result, a problem arises that the dimensions of the image pickup apparatus, in particular, the dimension as viewed from a front side of the image pickup apparatus increases.
Further, in the above structures disclosed in JP-A 2003-315861 and JP-A 2003-149723, the operations of the lens groups become complicated, inducing the lens barrier covering the front side of the lenses to easily interfere with the collapsing type lens barrel when the lens barrel shifts towards the collapsed and stored state.
Also, according to the structure disclosed in JP-A 2001-228507, there is a problem that its structure is difficult to be applied to the camera other than the manual open-close barrier type, since there is a variation in the engagement between the protrusion on the back surface of the external barrier and the protrusion on the front cover. In addition, it is necessary to separately manufacture the protrusions as components when a metal material is used for the external barrier and the front cover. Therefore, there is also a problem in JP-A 2001-228507 that a cost of the entire camera increases since the processes for manufacturing the protrusions as components and attaching each of the protrusions to the back surface of the external barrier and front of the front cover increase.
According to the structure disclosed in JP-A 2001-290196, since the front cover of the camera body and the external barrier are always attached to each other, there is a problem that it is necessary to increase a driving force of an actuator in the automatic open-close barrier type in a case where the actuator is driven by the main switch to open and close the external barrier. Thereby, a problem also arises in JP-A 2001-290196 that an operation of the camera including the external barrier tends to be uncertain and requires higher power consumption.
Furthermore, since JP-A 2001-91993 does not disclose measures for preventing the rattling movement between the front cover and the body barrier, the structure disclosed therein cannot solve the above-mentioned problems.